definition of
knock

[1] #1 knock v. [strike hard] deliver a sharp blow or push :"He knocked the glass clear across the room". wn

[2] #2 knock v. rap with the knuckles; "knock on the door". wn

[3] #3 knock v. [bump] knock against with force or violence; "My car bumped into the tree". wn

[4] #4 knock n. [knocking] the sound of knocking (as on a door or in an engine or bearing); "the knocking grew louder". wn

[5] #5 knock n. [roast] negative criticism. wn